R help - Jan 2012 - Sum of a couple of variables of which a few have NA values

Dear everyone,

I have looked all over the internet but I cannot find a way to solve my problem.

In my data I want to sum a couple of variables. Some of these
variables have NA values, and when I add them together, the result is
NA

dat <- data.frame(
id = gl(5,1),
var1 = rnorm(5, 10),
var2 = rnorm(5, 7),
var3 = rnorm(5, 6),
var4 = rnorm(5, 3),
var5 = rnorm(5, 8)
)
dat[3,3] <- NA
dat[4,5] <- NA
> dat
?id ? ? ?var1 ? ? var2 ? ? var3 ? ? var4 ? ? var5
1 ?1 ?9.371328 7.830814 5.032541 3.491053 7.626418
2 ?2 10.413516 7.333630 6.557178 1.465597 8.591770
3 ?3 10.967073 ? ? ? NA 6.674079 3.946451 7.251263
4 ?4 ?9.900380 7.727111 5.059698 ? ? ? NA 6.632962
5 ?5 ?9.191068 7.901271 6.652410 2.734856 8.484757

attach(dat)

dat$sum <- var2 + var3 + var4 # I think I'm doing this wrong, but I
don't know what command to use
> dat
  id      var1     var2     var3     var4     var5      sum
1  1  9.371328 7.830814 5.032541 3.491053 7.626418 16.35441
2  2 10.413516 7.333630 6.557178 1.465597 8.591770 15.35640
3  3 10.967073       NA 6.674079 3.946451 7.251263       NA
4  4  9.900380 7.727111 5.059698       NA 6.632962       NA
5  5  9.191068 7.901271 6.652410 2.734856 8.484757 17.28854

I would like to omit the values of NA and just sum the rest.

I tried to use rowSums() but that sums an entire row and I only need a
few variables.

Does anyone know how to do this?

Thanks in advance,
Petra

x = runif(10)
x[4] = NA
sum(x, na.rm = T)

--
View this message in context:
http://r.789695.n4.nabble.com/Sum-of-a-couple-of-variables-of-which-a-few-have-NA-values-tp4282448p4282483.html
Sent from the R help mailing list archive at Nabble.com.

Hi Petra,

Try this:
dat$sums <- rowSums(dat[3:5], na.rm=TRUE)

I think this should do what you're looking for
HTH,
Ivan

-------- Message original --------
Sujet: 	[R] Sum of a couple of variables of which a few have NA values
Date : 	Tue, 10 Jan 2012 17:25:21 +0100
De : 	Petra Opic <petraopic at gmail.com>
Pour : 	r-help at r-project.org



Dear everyone,

I have looked all over the internet but I cannot find a way to solve my problem.

In my data I want to sum a couple of variables. Some of these
variables have NA values, and when I add them together, the result is
NA

dat<- data.frame(
id = gl(5,1),
var1 = rnorm(5, 10),
var2 = rnorm(5, 7),
var3 = rnorm(5, 6),
var4 = rnorm(5, 3),
var5 = rnorm(5, 8)
)
dat[3,3]<- NA
dat[4,5]<- NA
>  dat
  id      var1     var2     var3     var4     var5
1  1  9.371328 7.830814 5.032541 3.491053 7.626418
2  2 10.413516 7.333630 6.557178 1.465597 8.591770
3  3 10.967073       NA 6.674079 3.946451 7.251263
4  4  9.900380 7.727111 5.059698       NA 6.632962
5  5  9.191068 7.901271 6.652410 2.734856 8.484757

attach(dat)

dat$sum<- var2 + var3 + var4 # I think I'm doing this wrong, but I
don't know what command to use
>  dat
   id      var1     var2     var3     var4     var5      sum
1  1  9.371328 7.830814 5.032541 3.491053 7.626418 16.35441
2  2 10.413516 7.333630 6.557178 1.465597 8.591770 15.35640
3  3 10.967073       NA 6.674079 3.946451 7.251263       NA
4  4  9.900380 7.727111 5.059698       NA 6.632962       NA
5  5  9.191068 7.901271 6.652410 2.734856 8.484757 17.28854

I would like to omit the values of NA and just sum the rest.

I tried to use rowSums() but that sums an entire row and I only need a
few variables.

Does anyone know how to do this?

Thanks in advance,
Petra

______________________________________________
R-help at r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.




-- 
Ivan CALANDRA
Universit? de Bourgogne
UMR CNRS 5561 Biog?osciences
6 Boulevard Gabriel
21000 Dijon, FRANCE
ivan.calandra at u-bourgogne.fr

On Jan 10, 2012, at 11:25 AM, Petra Opic wrote:
> Dear everyone,
>
> I have looked all over the internet but I cannot find a way to solve  
> my problem.
? rowSums   # has an na.rm argument
>
> In my data I want to sum a couple of variables. Some of these
> variables have NA values, and when I add them together, the result is
> NA
snip
> attach(dat)
You would be well-advised to forget `attach`. Use with(dat, ...)  
instead. It will prevent frustration and embarrassing postings to rhelp.
>
> dat$sum <- var2 + var3 + var4
The plus infix operator does not have an na.rm argment

dat$sum <- rowSums(dat[ , 2:4] , na.rm=TRUE)

-- 

David Winsemius, MD
West Hartford, CT

Dear Ivan,

Thank you very much for your help.

How do I use rowSums if I need to "skip" a variable from summing?
(example:
sum var1, var2, var3, var5, var34 only).

Thanks in advance,
Petra Opic

--
View this message in context:
http://r.789695.n4.nabble.com/Sum-of-a-couple-of-variables-of-which-a-few-have-NA-values-tp4282448p4282969.html
Sent from the R help mailing list archive at Nabble.com.